Re: [Xen-users] Xen, NFS performance, rsize, wsize and MTU

[Richard Jones <rich@xxxxxxxxxxx>]

On Fri, Feb 17, 2006 at 08:34:00PM +0000, Ceri Storey wrote:
> On Fri, Feb 17, 2006 at 02:41:12PM +0000, Richard Jones wrote:
> > We have a Xen 3.0 / Linux kernel 2.6.15 machine with the domU's
> > configured for shared /home directories.  One of the domU's is an NFS
> > server, exporting /home, and the other domU's all mount this.
> 
> > It all functions fine, but it's pretty slow.
> 
> > I tried untarring a recent Linux kernel tarball.  On the NFS server
> > domU this takes about 25 seconds.  I didn't wait long enough to find
> > out how long it was going to take on the NFS client domU's - I killed
> > it after 15 minutes.
> 
> How many CPUs does this server have? If you've got a single CPU (sans
> hyperthreading) machine then, there'll be the overhead of at least ~4 context
> switches per request to deal with (the domU sends the initial request packet, 
> which
> is bridged / routed via dom0, which sends it to the NFS server domU,
> and, then back agan). 

You're right and it is a single processor machine.  I'm not expecting
blazing performance (we far prefer reliability / predictability).
It's just really is quite slow at the moment and I'm sure that it's
down to some sort of configuration mistake.

Rich.

-- 
Richard Jones, CTO Merjis Ltd.
Merjis - web marketing and technology - http://merjis.com
Team Notepad - intranets and extranets for business - http://team-notepad.com

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